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Showing papers on "Lift-induced drag published in 1979"


Journal ArticleDOI
TL;DR: In this paper, the authors studied the dynamics of lift and thrust generation by flying animals by considering the distribution of vorticity in the wake of flying animals, and derived the induced power as the rate of increase of wake kinetic energy.
Abstract: The mechanics of lift and thrust generation by flying animals are studied by considering the distribution of vorticity in the wake As wake generation is not continuous, the momentum jet theory, which has previously been used, is not satisfactory, and the vortex theory is a more realistic model The vorticity shed by the wings in the course of each powered stroke deforms into a small-cored vortex ring; the wake is a chain of such rings The momentum of each ring sustains and propels the animal; induced power is calculated as the rate of increase of wake kinetic energy A further advantage of the vortex theory is that lift and induced drag coefficients are not required; estimated instantaneous values of these coefficients are generally too large for steady state aerodynamic theory to be appropriate to natural flapping flight The vortex theory is applied to hovering of insects and to avian forward flight A simple expression for induced power in hovering is found Induced power is always greater than simple momentum jet estimates, and the discrepancy becomes substantial as body mass increases In hovering the wake is composed of a stack of horizontal, coaxial, circular vortex rings In forward flight of birds the rings are elliptic; they are neither horizontal nor coaxial because the momentum of each ring balances the vector sum of parasite and profile drag and the bird9s weight Total power consumption as a function of flight velocity is calculated and compared for several species Power reduction is one of the major factors influencing the choice of flight style A large body of data is used to obtain an approximate scaling between stroke period and the body mass for birds Together with relations between other morphological parameters, this is used to estimate the variation of flight speed and power with body mass for birds, and on this basis deviations from allometric scaling can be related to flight proficiency and to the use of such strategies as the bounding flight of small passerines Note: Present address: Department of Zoology, University of Bristol, Woodland Road, Bristol BS8 IUG, UK

332 citations


Journal ArticleDOI
TL;DR: In this paper, the authors modeled the vortex wake of a bird in steady forward flight as a chain of elliptical vortex rings, each generated by a single downstroke, and determined the shape and inclination of each ring by the downstroke geometry, and the size of each circle by the wing circulation.
Abstract: The vortex wake of a bird in steady forward flight is modelled by a chain of elliptical vortex rings, each generated by a single downstroke. The shape and inclination of each ring are determined by the downstroke geometry, and the size of each ring by the wing circulation; the momentum of the ring must overcome parasitic and profile drags and the bird's weight for the duration of a stroke period. From the equation of motion it is possible to determine exactly the kinematics of the wing-stroke for any flight velocity. This approach agrees more readily with the nature of the wing-stroke than the classical actuator disk and momentum-jet theory; it also dispenses with lift and induced drag coefficients and is not bound by the constraints of steady-state aerodynamics. The induced power is calculated as the mean rate of increase of wake kinetic energy. The remaining components of the flight power (parasite and profile) are calculated by traditional methods; there is some consideration of different representations of body parasite drag. The lift coefficient required for flight is also calculated; for virtually all birds the lift coefficient in slow flight and hovering is too large to be consistent with steady-state aerodynamics. A bird is concerned largely to reduce its power consumption on all but the shortest flights. The model suggests that there are a number of ways in which power reduction can be achieved. These various strategies are in good agreement with observation.

188 citations


01 Dec 1979
TL;DR: In this paper, it was shown that the distribution of lift which causes the least drag is reduced to the solution of the problem for systems of airfoils which are situated in a plane perpendicular to the direction of flight.
Abstract: Equations are derived to demonstrate which distribution of lifting elements result in a minimum amount of aerodynamic drag. The lifting elements were arranged (1) in one line, (2) parallel lying in a transverse plane, and (3) in any direction in a transverse plane. It was shown that the distribution of lift which causes the least drag is reduced to the solution of the problem for systems of airfoils which are situated in a plane perpendicular to the direction of flight.

183 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that by cooling laminar boundary layers in air at subsonic and low supersonic speeds, they are more stable than adiabatic boundary layers and therefore more resistant to transition to turbulent flow.
Abstract: Drag reductions are possible for cryo-fueled aircraft by using fuel to cool selected aerodynamic surfaces on its way to the engines. This is because cooled laminar boundary layers in air at subsonic and low supersonic speeds are more stable than adiabatic boundary layers and therefore more resistant to transition to turbulent flow. Calculations for A/=0.85 hydrogen-fueled transport show that drag reductions in cruise of about 20% are within reason. The weight of the fuel saved is well in excess of the weight of the required cooling system. These results suggest that the hydrogen fueled aircraft employing surface cooling is quite attractive as an energy conservative aircraft and warrants more detailed study.

48 citations



Journal ArticleDOI
TL;DR: In this article, three different types of base cavities, one solid walled and two ventilated, each with six different depths ranging from 0.1 to 0.9 body diameters, were evaluated for axisymmetric bodies.
Abstract: Base cavities (hollow extensions mounted behind the rear end of a bluff body) are known to reduce substantially the aerodynamic drag of two-dimensional bodies. For axisymmetric bodies their effect is not well established, and the objective of this work was to assess their drag-reducing potential. Experiments were performed using three different types of base cavities, one solid walled and two ventilated, each with six different depths ranging from 0.1 to 0.9 body diameters. All three types of cavities reduced the body drag for small cavity depths, with a maximum drag coefficient reduction of 0.027 being obtained with a ventilated cavity 0.2 diameters deep. The reductions are an order of magnitude lower than those reported for two-dimensional bodies, but are achieved with a much shorter cavity depth. Although the ventilated cavities had a beneficial effect for small depths, at large depths (greater than 0.5 diameters) they had an opposite effect – a very large drag increase. The cause of this increase is as yet not understood. Hot-wire investigation revealed that base cavities suppress wake periodicity. For cavities of small depth this correlated with a reduction in drag, but for large cavity depths the trends of the intensity of the periodic motion and of drag were not always the same.

36 citations


Journal ArticleDOI
Julian Wolkovitch1
TL;DR: In this paper, the authors used wind-tunnel tests to check the Prandtl-Munk theory for a configuration with equal-span tandem wings with gap/span = 0.25, and a stagger/span= 0.44.
Abstract: The Prandtl-Munk theory predicts that tandem-wing configurations with large (vertical) gap have substantially lower induced drag than conventional wing-tail configurations of similar span, total lift, and dynamic pressure. Wind-tunnel tests were performed to check the theory for a configuration with equal-span tandem wings with gap/span = 0.25, and a stagger/span = 0.44. The tests show that the tandem-wing induced drag is even lower than theoretically predicted values. The application of tandem wings to VSTOL subsonic aircraft is discussed, and a new type of tandem-wing configuration is described. This employs extreme gull-type dihedral and anhedral on the rear wing. This feature reduces induced drag, and also reduces wetted area by eliminating the need for a separate vertical tail. Nomenclature

26 citations


01 Nov 1979
TL;DR: In this paper, the suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component was discussed, and a series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.
Abstract: Exploratory wind tunnel tests are reported on a 74 deg. delta wing model. The potential of a vortex flap concept in reducing the subsonic lift dependent drag of highly swept, slender wings is examined. The suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component is discussed. A series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.

23 citations


01 Jan 1979
TL;DR: An upper surface modification designed to increase the maximum lift coefficient of a 63 sub 2 - 215 airfoil section was tested at Mach numbers of 0.2, 0.3, and 0.4 Reynolds numbers of 1.3x 1 million, 2 x 10 sub 6 and 2.5 x 1 million as mentioned in this paper.
Abstract: An upper surface modification designed to increase the maximum lift coefficient of a 63 sub 2 - 215 airfoil section was tested at Mach numbers of 0.2, 0.3, and 0.4 Reynolds numbers of 1.3 x 1 million, 2 x 10 sub 6 and 2.5 x 1 million. Comparisons of the aerodynamic coefficients before and after the modification were made. The upper surface modification increased the maximum lift coefficient of the airfoil significantly at all conditions.

21 citations


Patent
28 Sep 1979
TL;DR: In this article, a family of airfoils for use in rotary wing aircraft, particularly helicopters, is described, characterized by having a maximum c 1.sbsb.max at M = 0.4 and maximum delay in drag divergence while maintaining zero lift pitching moment levels c m.sb.o correctable within the range of -0.01 to +0.
Abstract: A family of airfoils for use in rotary wing aircraft, particularly helicopters, is disclosed. The family is characterized by having a maximum c 1 .sbsb.max at M=0.4 and maximum delay in drag divergence while maintaining zero lift pitching moment levels c m .sbsb.o correctable within the range of -0.01 to +0.01. The present family of airfoils provide high lift at maximum angle of attack when the blade is retreating and maximum delay in drag rise or drag divergence when the blade is advancing. The airfoil section of the family enable a helicopter rotor to counteract, more efficiently, the rolling moment which would otherwise be induced by a rotorcraft's forward flight; this is achieved by the present family of airfoils while maintaining the airfoil sectional pitching moment coefficient at or about zero thereby enabling the blade in which the airfoil sections are incorporated to impose minimum structural loads on the rotorcraft's control system.

20 citations


Proceedings ArticleDOI
01 Jul 1979
Abstract: This paper contains a number of examples wherein basic aerodynamic shapes are shown to achieve improved performance when non-linear effects are taken into account. Analytical, numerical, and experimental results have all been used to demonstrate this conclusion. Improvements in both zero lift drag and drag due to lift have been identified. The results show that the exploitation of these non-linear aerodynamic effects may be a key ingredient of future supersonic aircraft.

Journal ArticleDOI
TL;DR: In this paper, an investigation was conducted in the Langley 16ft transonic tunnel to further study benefits in climb and cruise performance due to blowing the jet over the wing for a transport-type wing-body configuration.
Abstract: An investigation was conducted in the Langley 16-ft transonic tunnel to further study benefits in climb and cruise performance due to blowing the jet over the wing for a transport-type wing-body configuration. In this investigation, a wing-body model powered-nacelle test rig combination was tested at Mach numbers of 0.5 and 0.8 at angles of attack from — 2-4 deg and jet total-pressure ratios from jet off to 3 or 4 (depending on Mach number) for a variety of nacelle locations relative to the wing. Results from this investigation show that positioning of the nacelles can have very large effects on the wing-body drag (nacelles were nonmetric). Some positions yielded much higher drag than the baseline wing-body, while others yielded drag somewhat lower than the baseline. Nomenclature CD = drag coefficient CL = lift coefficient Cm = pitching moment coefficient D — jet-exit diameter JO - jet off LE = leading edge M = Mach number NPR = nozzle pressure ratio—ratio of jet total-pressure to freestream static pressure x — position of nacelle exit with respect to wing leading edge-positive aft W-B = wing-body wrt = with respect to z = height of centerline of nacelle exit above wing chord plane a = angle of attack

01 Apr 1979
TL;DR: In this article, a wind tunnel test utilizing a 4.7 percent scale semi-span model in the Langley Research Center 8-foot transonic pressure wind tunnel was conducted to evaluate the performance of the DC-10 wide body transport aircraft.
Abstract: Results are presented of a wind tunnel test utilizing a 4.7 percent scale semi-span model in the Langley Research Center 8-foot transonic pressure wind tunnel to establish the cruise drag improvement potential of winglets as applied to the DC-10 wide body transport aircraft. Winglets were investigated on both the DC-10 Series 10 (domestic) and 30/40 (intercontinental) configurations and compared with the Series 30/40 configuration. The results of the investigation confirm that for the DC-10 winglets provide approximately twice the cruise drag reduction of wing-tip extensions for about the same increase in bending moment at the wing fuselage juncture. Furthermore, the winglet configurations achieved drag improvements which were in close agreement to analytical estimates. It was observed that relatively small changes in wing-winglet tailoring effected large improvements in drag and visual flow characteristics. All final winglet configurations exhibited visual flow characteristics on the wing and winglets

01 Jan 1979
TL;DR: In this article, the operational characteristics of a double-membraned sailwing were discussed with emphasis placed on the importance of the trailing edge cable tension, and three dimensional aerodynamic characteristics were obtained from wind tunnel tests, and the results compared to determine the magnitude of the aerodynamic penalties paid for various structural simplifications.
Abstract: The operational characteristics of sailwings are discussed with emphasis placed on the importance of the trailing edge cable tension. The three dimensional aerodynamic characteristics were obtained from wind tunnel tests, and the results compared to determine the magnitude of the aerodynamic penalties paid for various structural simplifications. For the sectional thickness ratios, it is concluded that, while the basic double-membraned sailwing has exceptional aerodynamic performance, even superior for some applications to the conventional hardwing, any notable deviation from this configuration results in an unacceptably large performance penalty.

01 Jul 1979
TL;DR: In this article, a combined analytical and experimental modeling study was initiated to investigate the flow field in the vicinity of thru hole type damages on lifting surfaces, and a promising aeroelastic failure mechanism was identified that results from the localized drag generated when a lifting surface encounters severe damage to its aerodynamic shape.
Abstract: : An investigation is carried out to determine whether ballistic damage can seriously degrade the aeroelastic integrity of lifting surfaces on aircraft A promising aeroelastic failure mechanism is identified that results from the localized drag generated when a lifting surface encounters severe damage to its aerodynamic shape This damage induced drag is shown to significantly decrease the divergence speed of a generic or statistical fighter wing for certain damage site locations while increasing the flutter speed of the wing Consequently, a critical damage level exits where divergence becomes the critical aeroelastic instability for a wing which may still have adequate strength and flutter integrity In view of the very limited information existing on the aerodynamic modeling of damaged lifting surfaces, a combined analytical and experimental modeling study was initiated to investigate the flow field in the vicinity of thru hole type damages on lifting surfaces (Author)

01 Jun 1979
TL;DR: In this paper, exact analytical solutions in terms of induced drag influence coefficients can be attained which define the spanwise loading with minimized induced drag, subject to specified constraint conditions, for any nonplanar wing shape or number of lift plus wing bending moment about a given wing span station.
Abstract: Exact analytical solutions in terms of induced drag influence coefficients can be attained which define the spanwise loading with minimized induced drag, subject to specified constraint conditions, for any nonplanar wing shape or number of lift plus wing bending moment about a given wing span station. Example applications of the theory are made to a biplane, a wing in ground effect, a cruciform wing, a V-wing, a planar-wing winglet, and linked wingtips in formation flying. For minimal induced drag, the spanwise loading, relative to elliptic, is outboard for the biplane and is inboard for the wing in ground effect and for the planar-wing winglet. A spinoff of the triplane solution provides mathematically exact equations for downwash and sidewash about a planar vorticity sheet having an arbitrary loading distribution.

01 Jun 1979
TL;DR: In this paper, a theoretical method was developed for determining the optimum span load distribution for minimum induced drag for subsonic nonplanar configurations, where undistorted wing wake is assumed to have piecewise linear variation of shed vortex sheet strength, resulting in a quadratic variation of bound circulation and span load.
Abstract: A theoretical method was developed for determining the optimum span load distribution for minimum induced drag for subsonic nonplanar configurations. The undistorted wing wake is assumed to have piecewise linear variation of shed vortex sheet strength, resulting in a quadratic variation of bound circulation and span load. The optimum loading is obtained either through a direct technique, whereby derivatives of the drag expression are calculated analytically in terms of the unknown wake vortex sheet strengths. Both techniques agree well with each other and with available exact solutions for minimum induced drag.

01 Nov 1979
TL;DR: In this article, the design of an aircraft which employs an integrated wing and winglet lift system was presented, and an optimized wing-winglet combination was selected from four proposed configurations for which aerodynamic, structural, and weight characteristics were evaluated.
Abstract: The design is presented of an aircraft which employs an integrated wing and winglet lift system. Comparison was made with a conventional baseline configuration employing a high-aspect-ratio supercritical wing. An optimized wing-winglet combination was selected from four proposed configurations for which aerodynamic, structural, and weight characteristics were evaluated. Each candidate wing-winglet configuration was constrained to the same induced drag coefficient as the baseline aircraft. The selected wing-winglet configuration was resized for a specific medium-range mission requirement, and operating costs were estimated for a typical mission. Study results indicated that the wing-winglet aircraft was lighter and could complete the specified mission at less cost than the conventional wing aircraft. These indications were sensitive to the impact of flutter characteristics and, to a lesser extent, to the performance of the high-lift system. Further study in these areas is recommended to reduce uncertainty in future development.


Proceedings ArticleDOI
01 Aug 1979
TL;DR: In this paper, the effect of the cooling air flow through the nacelle was measured in the NASA-Ames 40- by 80 foot wind tunnel of a wing semispan with a nacelles from a typical, general aviation twin-engine aircraft.
Abstract: Tests were made in the NASA-Ames 40- by 80 Foot Wind Tunnel of a wing semispan with a nacelle (no propeller) from a typical, general aviation twin-engine aircraft. Measurements were made of the effect on drag of the cooling air flow through the nacelle. Internal and external nacelle pressures were measured. It was found that the cooling flow accounts for about 13% of the estimated airplane drag and about 42% of the cooling flow drag is associated with the internal flow. It was concluded that improvements could be made by relocating both the inlet and the outlet of the cooling air.

01 Dec 1979
TL;DR: In this article, the aerodynamic design of a wind-tunnel model of a wing representative of that of a subsonic jet transport aircraft, fitted with winglets, was performed using two recently developed optimal wing-design computer programs.
Abstract: The aerodynamic design of a wind-tunnel model of a wing representative of that of a subsonic jet transport aircraft, fitted with winglets, was performed using two recently developed optimal wing-design computer programs. Both potential flow codes use a vortex lattice representation of the near-field of the aerodynamic surfaces for determination of the required mean camber surfaces for minimum induced drag, and both codes use far-field induced drag minimization procedures to obtain the required spanloads. One code uses a discrete vortex wake model for this far-field drag computation, while the second uses a 2-D advanced panel wake model. Wing camber shapes for the two codes are very similar, but the resulting winglet camber shapes differ widely. Design techniques and considerations for these two wind-tunnel models are detailed, including a description of the necessary modifications of the design geometry to format it for use by a numerically controlled machine for the actual model construction.

Proceedings ArticleDOI
15 Jan 1979
TL;DR: In this article, general integral expressions are derived for the nonlinear lift and pitching moment of arbitrary wing planforms in subsonic flow. The analysis uses the suction analogy and an assumed pressure distribution based on classical linear theory results.
Abstract: General integral expressions are derived for the nonlinear lift and pitching moment of arbitrary wing planforms in subsonic flow. The analysis uses the suction analogy and an assumed pressure distribution based on classical linear theory results. The potential flow lift constant and certain wing geometric parameters are the only unknowns in the integral expressions. Results of the analysis are compared with experimental data and other numerical methods for several representative wings, including ogee and double-delta planforms. The present method is shown to be as accurate as other numerical schemes for predicting total lift, induced drag, and pitching moment. b c c CL CD Cm CT Cs cc, ccd E2 Nomenclature = aspect ratio = wing span =chord = reference length = lift coefficient = drag coefficient = pitching moment coefficient = thrust coefficient = suction coefficient = section lift coefficient = section induced drag coefficient = section suction coefficient = pressure loading coefficient = drag = proportionality constant, Eq. (32) = proportionality constant, Eq. (53) = chordwise function, Eq. (44) ff(rj) = span wise f unction, Eq. (28) K = potential constant L =lift loading constant, Eq. (5) S = suction force SR = reference area s = suction force per unit length T = leading edge thrust, Eq. (7) T' = leading edge thrust per unit length V = freestream speed Wj = downwash velocity component, Eq. (11) a. = angle of attack F = vorticity p = freestream density £ = nondimensional chordwise coordinate 77 = nondimensional spanwise coordinate A = leading edge sweep angle Subscripts P = potential flow E =edge / = induced VLE = leading edge vortex VSE = side edge vortex

01 Apr 1979
TL;DR: The design and analysis of a supersonic transport configuration was conducted using linear theory methods in conjunction with appropriate constraints and indicated an improvement in lift-to-drag ratio.
Abstract: The design and analysis of a supersonic transport configuration was conducted using linear theory methods in conjunction with appropriate constraints. Wing optimization centered on the determination of the required twist and camber and proper integration of the wing and fuselage. Also included in the design are aerodynamic refinements to the baseline wing thickness distribution and nacelle shape. Analysis to the baseline and revised configurations indicated an improvement in lift-to-drag ratio of 0.36 at the Mach 2.7 cruise condition. Validation of the design is planned through supersonic wing tunnel tests.

Patent
27 Feb 1979

H. Zimmer1
01 Oct 1979
TL;DR: In this article, the necessary compromises between wing and configuration modifications which better lift performance and the weight gains accompanying such modifications are discussed, and applications of wing and modifications to advanced technology commercial aviation aircraft and the Airbus A-300 are mentioned.
Abstract: Lift-dependent induced drag in commercial aviation aircraft is discussed, with emphasis on the necessary compromises between wing and configuration modifications which better lift performance and the weight gains accompanying such modifications. Triangular, rectangular and elliptical configurations for wing ends are considered; attention is also given to airfoil designs incorporating winglets. Water tunnel tests of several configurations are reported. In addition, applications of wing and modifications to advanced technology commercial aviation aircraft and the Airbus A-300 are mentioned.

Proceedings ArticleDOI
01 Aug 1979
TL;DR: In this paper, the energy and economic benefits of low-speed aerodynamic system technology applied to a modern 200-passenger, 2000-nmi range, twin engine jet transport are reviewed.
Abstract: The energy and economic benefits of low-speed aerodynamic system technology applied to a modern 200-passenger, 2000-nmi range, twin engine jet transport are reviewed. Results of a new method to design flap systems at flight Reynolds number are summarized. The study contains the airplane high lift configuration drag characteristics and design selection charts showing the effect of flap technology on the airplane size and performance. The study areas include: wing and flap geometry, climb and descent speed schedules with partial flap deflection, flap system technology, and augmented stability. The results compare the improvements in payload from a hot, high elevation airport.

01 Jun 1979
TL;DR: In this article, a large-scale, tilt-nacelle V/STOL propulsion system was tested in the Ames 40 by 80 foot wind tunnel to determine its aerodynamic characteristics.
Abstract: Tests were performed in the Ames 40 by 80 Foot Wind Tunnel on a large-scale, tilt-nacelle V/STOL propulsion system to determine its aerodynamic characteristics. Unpowered nacelle aerodynamics and power induced effects over an angle of attack range from 0 to 105 deg are presented. It is shown that: (1) the characteristics of the unpowered nacelle can be estimated with annular airfoil data, (2) the power-induced effects on the nacelle aerodynamics are significant, and (3) pitching moment can be correlated with lift and thrust.

Proceedings ArticleDOI
06 Aug 1979
TL;DR: In this article, an analytical technique is presented which establishes the relationship between aerodynamic characteristics and total mission performance for ramjet-powered missiles which are launched at low altitude and must climb to high altitude for a long-range cruise at supersonic speeds.
Abstract: An analytical technique is presented which establishes the relationship between aerodynamic characteristics and total mission performance for ramjet-powered missiles which are launched at low altitude and must climb to high altitude for a long-range cruise at supersonic speeds. The analytical expressions obtained can be used to determine desirable aerodynamic characteristics and their variation with velocity given missile propulsion and design parameters such as specific fuel consumption, thrust coefficient, planform area, nozzle exit area, and weight. The expressions are derived for Rutowski minimum fuel-to-climb profiles and optimum specific fuel consumption cruise conditions. The low-altitude segment of the climb is shown to be dominated by the drag coefficient CD . and its variation with velocity. At high altitudes during the climb, the induced drag factor K becomes important. Therefore, reducing Q>min at low supersonic speeds and K at high supersonic speeds reduces fuel consumption during the climb. The desirable lift coefficient at minimum drag CL() is shown to be small at low speeds and to increase with velocity. The ideal climb-cruise configuration will have a Q>mjn and K which are low at low speeds and decrease strongly with increasing speed. The CL() will also be low at low speed but increase greatly with increasing speed. These results and the analytical expressions derived can be used by the missile designer as aerodynamic design criteria during configuration development.

01 Mar 1979
TL;DR: In this article, the effects of over-wing blowing jets on the induced drag of a 50 deg sweep back wing was analyzed and the mechanisms through which this drag reduction is brought about are presented.
Abstract: The results of two separate theoretical investigations are presented. A program was used which is capable of predicting the aerodynamic characteristics of both upper-surface blowing (USB) and over-wing blowing (OWB) configurations. A theoretical analysis of the effects of over-wing blowing jets on the induced drag of a 50 deg sweep back wing was developed. Experiments showed net drag reductions associated with the well known lift enhancement due to over-wing blowing. The mechanisms through which this drag reduction is brought about are presented. Both jet entrainment and the so called wing-jet interaction play important roles in this process. The effects of a rectangular upper-surface blowing jet were examined for a wide variety of planforms. The isolated effects of wing taper, sweep, and aspect ratio variations on the incremental lift due to blowing are presented. The effects of wing taper ratio and sweep angle were found to be especially important parameters when considering the relative levels of incremental lift produced by an upper-surface blowing configuration.

Book ChapterDOI
TL;DR: In this paper, an experimental study of the interaction between moving dislocations and the Abrikosov vortices in the mixed state of a superconductor was carried out.
Abstract: The work has been aimed at an experimental study of the interaction between moving dislocations and the Abrikosov vortices in the mixed state of a superconductor To that end the abrupt change of the deforming stress was studied that occured during the transition of the specimen from the superconducting to the mixed state and vice versa, in samples deformed in tension at a rate of 7x10-4s-1 The transition was provoked by application of external fields of different orientation with respect to the tensile axis Objects of the investigation were Pb - In alloys of various concentrations In the mixed state the magnitude of the abrupt stress changes shows considerable variations which have been attributed to the dislocation drag by the vortices The measured value normally is several tenths of 1 N/mm2 The experimental results are compared with calculated predictions for the vortex drag force due to lattice defects